RESUMEN
Oxide ceramics are considered promising candidates as solid electrolytes (SEs) for sodium metal batteries. However, the high sintering temperature induced boundaries and pores between angular grains lead to high grain boundary resistance and pathways for dendrite growth. Herein, we report a grain boundary modification strategy, which in situ generates an amorphous matrix among Na5SmSi4O12 oxide grains via tuning the chemical composition. The mechanical properties as well as electron mitigating capability of modified SE have been significantly enhanced. As a result, the SE achieves a room-temperature total ionic conductivity of 5.61 mS cm-1, the highest value for sodium-based oxide SEs. The Na|SE|Na symmetric cell achieves a high critical current density of 2.5 mA cm-2 and excellent cycle life over more than 2800 h at 0.15 mA cm-2 without dendrite formation. The full cell with Na3V2(PO4)3 as the cathode demonstrates impressive cycling performance, maintaining stability over 3000 cycles at 5C without observable loss of capacity.
RESUMEN
Solid-state potassium metal batteries are promising candidates for grid-scale energy storage due to their low cost, high energy density and inherent safety. However, solid state K-ion conductors struggle with poor ionic conductivity due to the large ionic radius of K+-ions. Herein, we report precise regulation of phase heterogeneity and reciprocity of the P2/P3-symbiosis K0.62Mg0.54Sb0.46O2 solid electrolyte (SE) for boosting a high ionic conductivity of 1.6×10-4 S cm-1 at 25 °C. The bulk ionic conducting mechanism is explored by elucidating the effect of atomic stacking mode within the layered framework on K+-ion migration barriers. For ion diffusion at grain boundaries, the P2/P3 biphasic symbiosis property assists in tunning the SE microstructure, which crystallizes in rod-like particles with lengths of tens of micrometers facilitating long-distance ion transport and significantly decreasing grain boundary resistance. Potassium metal symmetric cells using the modified SE deliver excellent cycling life over 300 h at 0.1 mA cm-2 and a high critical current density of 0.68 mA cm-2. The quasi-solid-state potassium metal batteries (QSSKBs) coupled with two kinds of layered oxide cathodes demonstrate remarkable stability over 300 cycles, outperforming the liquid electrolyte counterparts. The QSSKB system provides a promising strategy for high-efficiency, safe, and durable large-scale energy storage.
RESUMEN
Exploiting solid electrolyte (SE) materials with high ionic conductivity, good interfacial compatibility, and conformal contact with electrodes is essential for solid-state sodium metal batteries (SSBs). Here we report a crystalline Na5SmSi4O12 SE which features high room-temperature ionic conductivity of 2.9 × 10-3 S cm-1 and a low activation energy of 0.15 eV. All-solid-state symmetric cell with Na5SmSi4O12 delivers excellent cycling life over 800 h at 0.15 mA h cm-2 and a high critical current density of 1.4 mA cm-2. Such excellent electrochemical performance is attributed to an electrochemically induced in-situ crystalline-to-amorphous (CTA) transformation propagating from the interface to the bulk during repeated deposition and stripping of sodium, which leads to faster ionic transport and superior interfacial properties. Impressively, the Na|Na5SmSi4O12|Na3V2(PO4)3 sodium metal batteries achieve a remarkable cycling performance over 4000 cycles (6 months) with no capacity loss. These results not only identify Na5SmSi4O12 as a promising SE but also emphasize the potential of the CTA transition as a promising mechanism towards long-lasting SSBs.